External resonator-type wavelength tunable laser device

Abstract

The present invention provides an external resonator-type wavelength tunable laser device that can properly fulfill a wavelength tuning function even with the use of a planar wavelength tunable reflector involving a considerable level of residual reflection. The external resonator-type wavelength tunable laser device includes a planar reflection structure enabling a reflection spectral peak wavelength to be varied and a semiconductor element as a semiconductor gain medium. The semiconductor gain medium is composed of a multiple quantum well in which product Γ·L of optical confinement constant Γ and semiconductor gain medium length L (μm) of a gain layer is at least 25 μm and at most 40 μm and in which gain peak wavelength λ0 (nm) observed during carrier injected with a maximum modal gain equal to an internal loss of the semiconductor gain medium is larger than −3·ΔR / 2+(λc+35) and smaller than (−(Γ·L) / 7+8)·ΔR+(−(Γ·L)+λc+45). Here, ΔR (dB) denotes a reflectance difference, and λc (nm) denotes a wavelength at a center of an operating wavelength range of the wavelength tunable laser device.

Description

[0001]The present application is the National Phase of PCT / JP2008 / 059446, filed May 22, 2008, which claims a priority based on Japanese Patent Laid-Open No. 2007-156214 filed on Jun. 13, 2007, and incorporates the entire disclosure thereof.TECHNICAL FIELD[0002]The present invention relates to an external resonator-type wavelength tunable laser device including a planar reflection structure enabling a reflection spectral peak wavelength to be varied, and a semiconductor optical amplifier contained in the wavelength tunable laser device to use as a semiconductor gain medium.BACKGROUND ART[0003]With the recent rapid prevalence of the Internet, there has been a demand for a further increase in the capacity of communication traffic. To deal with this, efforts have been made, in the field of optical communication systems, to increase the number of available channels by improving the transmission rate per channel and by utilizing a wavelength division multiplexing (WDM) scheme.[0004]The WD...

AI Technical Summary

Benefits of technology

[0041]An object of the present invention is to provide an external resonator-type wavelength tunable laser device that can solve at least one of the above-described problems. An example of a specific object is to provide an external resonator-type wavelength tunable laser device that can properly fulfill a wavelength tuning function even with the use of a planar wavelength tunable reflector involving a considerable level of residual reflection. Another specific object is to provide a semiconductor optical amplifier serving as a component of the wavelength tunable laser device and corresponding to a semiconductor gain medium, in order to provide the wavelength tunable laser device.

Problems solved by technology

For example, 100 channels require the respective, 100 types of laser devices, resulting in an increase in the need for inventory control and an increase in inventory costs.

Thus, an increase in the number of laser elements arranged in parallel correspondingly increases the loss of the coupler.

However, it has been found that when a planar wavelength tunable reflector is used to construct an external resonator-type wavelength tunable laser device in an attempt to obtain wavelength tunable characteristics, the laser device may disadvantageously oscillate at a wavelength that is different from the reflection spectral peak of the wavelength tunable reflector used.

However, this is disadvantageous to the wavelength tunable laser device.

Thus, the wavelength tunable laser device with a wavelength tunable range of 30 nm to 35 nm or more fails to offer the possible range of gain peak wavelength λp of the semiconductor optical amplifier.

That is, the desired wavelength tunable range of the wavelength tunable laser device cannot be achieved.

It is thus very difficult to provide a wavelength tunable laser device with the desired wavelength tunable range based on the control only of gain peak wavelength λp of the semiconductor optical amplifier.

This problem is particularly significant when the wavelength tunable range of the wavelength tunable laser device is set to be equal to or wider than the range of about 30 nm to 35 nm, generally corresponding to a full band operation in one communication wavelength band.

However, in the planar reflection structure, setting ΔR to at least 20 dB is very difficult.

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